Method and apparatus for a self-cleaning filter

Abstract

A method and apparatus for removing fine particulate matter from a fluid stream without interrupting the overall process or flow. The flowing fluid inflates and expands the flexible filter, and particulate is deposited on the filter media while clean fluid is permitted to pass through the filter. This filter is cleaned when the fluid flow is stopped, the filter collapses, and a force is applied to distort the flexible filter media to dislodge the built-up filter cake. The dislodged filter cake falls to a location that allows undisrupted flow of the fluid after flow is restored. The shed particulate is removed to a bin for periodic collection. A plurality of filter cells can operate independently or in concert, in parallel, or in series to permit cleaning the filters without shutting off the overall fluid flow. The self-cleaning filter is low cost, has low power consumption, and exhibits low differential pressures.

What is claimed is: 
     
       1. A process for removing a particulate from a fluid stream, comprising:
 flowing a fluid stream containing a particulate through a fluid permeable, flexible filter in an upstream-to-downstream direction; 
 expanding the filter so as to provide a cavity at an upstream side of the filter; 
 depositing the particulate on an interior surface of the expanded filter, wherein the interior surface is at an interior of the cavity; 
 discontinuing the flow of the fluid steam through the filter; and 
 collapsing the filter in a downstream-to-upstream direction to convert the filter from the expanded state to an inverted state and thereby dislodge the particulate from the filter. 
 
     
     
       2. The process of  claim 1 , wherein expanding the filter comprises creating or increasing a pressure differential across the filter. 
     
     
       3. The process of  claim 2 , wherein collapsing the filter comprises removing or reducing the pressure differential across the filter. 
     
     
       4. The process of  claim 1 , wherein expanding the filter comprises extracting an energy from the fluid stream and storing the energy in a mechanical form. 
     
     
       5. The process of  claim 4 , wherein collapsing the filter comprises releasing the stored mechanical energy. 
     
     
       6. The process of  claim 1 , wherein flowing the fluid stream comprises controlling the fluid stream with a fluid control means disposed upstream of the filter, the fluid control means selected from the group consisting of a valve, a pump, a compressor, and a blower. 
     
     
       7. The process of  claim 1 , wherein flowing the fluid stream comprises controlling the fluid stream with a fluid control means disposed downstream of the filter, the fluid control means selected from the group consisting of a valve, a pump, a compressor, and a blower. 
     
     
       8. A self-cleaning filter apparatus for removing a particulate from a fluid stream flowing in an upstream-to-downstream direction, comprising:
 a first fluid-permeable, flexible filter having an expanded state and an inverted state, wherein, when the first filter is in the expanded state, a cavity is provided at an upstream side of the first filter and the first filter is configured to capture the particulate on an interior surface of the first filter that is at an interior of the cavity when receiving the fluid stream therethrough, and wherein, when the first filter is in the inverted state, the first filter is configured to dislodge the particulate from the interior surface; 
 a first force means configured to cooperate with the first filter, wherein the first force means is positioned and configured to apply a force sufficient to convert the first filter from the expanded state to the inverted state; 
 a second fluid-permeable, flexible filter having an expanded state and an inverted state, wherein, when the second filter is in the expanded state, a cavity is provided at an upstream side of the second filter and the second filter is configured to capture the particulate on an interior surface of the second filter that is at an interior of the cavity when receiving the fluid stream therethrough, and wherein, when the second filter is in the inverted state, the second filter is configured to dislodge the particulate from the interior surface; and 
 a second force means configured to cooperate with the second filter, wherein the second force means is positioned and configured to apply a force sufficient to convert the second filter from the expanded state to the inverted state. 
 
     
     
       9. The apparatus of  claim 8 , wherein each of the first and second force means is configured to extract an energy from the flowing fluid stream as it passes through the first or second filter, to store the energy in a mechanical form, and to release the stored mechanical energy to apply the force to the first or second filter, respectively. 
     
     
       10. The apparatus of  claim 8 , wherein the first filter is coupled with a tube sheet. 
     
     
       11. The apparatus of  claim 10 , wherein the first filter is free of any physical support structure, other than the tube sheet and the first force means. 
     
     
       12. The apparatus of  claim 8 , wherein the first force means comprises one or more members selected from the group consisting of a spring, a cable, a bladder, and a weight. 
     
     
       13. The apparatus of  claim 8 , wherein the first force means is coupled with the upstream side of the first filter, a downstream side of the first filter, or the upstream side of the first filter and the downstream side of the first filter. 
     
     
       14. The apparatus of  claim 8 , wherein the first filter comprises a membrane surface that is difficult for the particulate to adhere. 
     
     
       15. A method for removing a particulate from a fluid stream, comprising:
 flowing the fluid stream through a first self-cleaning fluid filter to capture a first portion of the particulate from the fluid stream; 
 stopping the fluid stream flow through the first fluid filter while flowing the fluid stream through a second self-cleaning fluid filter to capture a second portion of the particulate from the fluid stream; 
 discharging the first captured portion of particulate from the first fluid filter by applying a force to the fluid filter sufficient to convert the fluid filter from an expanded state to an inverted state; 
 stopping the fluid stream flow through the second filter; and 
 discharging the second captured portion of particulate from the second fluid filter. 
 
     
     
       16. The method of  claim 15 , wherein the first and second captured portions of particulates are discharged continuously, semi-continuously, or non-continuously. 
     
     
       17. The method of  claim 15 , comprising identifying an unclean self-cleaning fluid filter with a differential pressure sensor. 
     
     
       18. The method of  claim 15 , comprising determining a frequency of a cleaning cycle with a differential pressure sensor. 
     
     
       19. The method of  claim 15 , wherein discharging the first captured portion of particulate from the first fluid filter comprises collapsing the first fluid filter to distort an interior surface thereof. 
     
     
       20. The method of  claim 15 , further comprising:
 flowing the fluid stream through a third self-cleaning fluid filter to capture a third portion of the particulate from the fluid stream; 
 coordinating operation of the first, second, and third self-cleaning fluid filters; and 
 executing a cleaning cycle that involves only a portion of the first, second, and third self-cleaning fluid filters.